There are two scenarios for using the variable dispenser.

1. You want just one variable. In this scenario, call LockOneForRead or LockOneForWrite, and a collection with one element is returned.

2. You want several variables. In this scenario, call LockForRead and LockForWrite several times, one for each variable. This builds up two lists, one list that contains variables for reading and one list that contains variables for writing. Next, call GetVariables, which gives you a collection that contains all of the locked variables. If GetVariables succeeds, the two lists, which are the lists of variable names, not actual locks, are cleared.

To explicitly release the locks, call Unlock on the collection. This method unlocks the variables themselves. If GetVariables fails, the lists remain unchanged, and you can call GetVariables again. If you still do not succeed in obtaining the variables, call Reset to clear the lists and bring the variable dispenser back to its initial state.

The Variables collection contains a Locked property that indicates whether a variable dispenser collection of variables is locked (true) or unlocked (false). The reason to review this property is that some tasks explicitly release locks to the variables they are using, and calling Unlock twice throws an error. Therefore, you should use this property to determine whether the dispensed collection is locked before calling Unlock.

Important:
The VariableDispenser is used with the Runtime classes. If you are using data flow components (Microsoft.SqlServer.Dts.Pipeline), then you may be required to use the IDTSVariableDispenser100 instead. To know which variable dispenser to use, see the documentation for the object you are acquiring variables on, and verify the return object of the method.

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